Metric System & Density of Irregular Object
The purpose of this experiment is to become familiar with the metric
system by taking measurements with metric units. A second purpose
of this experiment is learn how to handle data collection and then
and the proper use of significant figures, proper unit usage and the
application of dimensional analysis.
and Materials (Total Time 90 - 120 min.)
mL grad cylinder
mL grad cylinder
ml grad cylinder
new #2 pencil
2-L bottle w/ cap
Observations are very important in chemistry experiments. Two types
of observations are qualitative and quantitative. Qualitative observations
are description of an observable property such as the color, odor, or
texture. Quantitative observations are numerical measurements and require
a number and a unit in order to be complete. For example, if your height
is six feet, then the number is "six", and the unit is "feet".
In scientific work, quantitative measurements are almost always recorded
in the units of the metric system.
work, the basic metric units of mass, length, and volume used are
the gram (g), the meter (m), and the liter (L),
respectively. Also commonly used in the laboratory, is the degree
Celsius (°C), which is the metric unit of temperature measurement.
convenience and consistency, metric units are subdivided by either
multiplication or division by some power of ten. The prefixes
deci-, centi-, and milli-, mean 1/10, 1/100,
and 1/1000 of the original unit, respectively. The prefix kilo-
and mega-, means 1000 and 1,000,000 times the original unit. Refer
to some tables (textbook, website …) containing the commonly
used units and their conversions.)
It is very
important to realize that whenever any measurement is made, some part
of the measurement is an estimation. Therefore, any measurement
always has some degree of uncertainty. For example, in
measuring the outside diameter of a test tube, as shown in Figure
1, you would record the diameter as 1.52 cm. The first two digits,
one and five, would be the same regardless of who made the measurement;
that is, they are certain. The third digit, two, however,
was determined by a visual estimate. This digit would
depend on who made the measurement; that is, it is uncertain.
Each number which is recorded, including all the certain numbers,
and the first uncertain number, are called significant figures.
The number of significant figures obtained in a measurement
will always be determined by the scale of the measuring device used.
Suppose that you are measuring the outside diameter of a coin shown
under the centimeter scale. The diameter is recorded as 1.52
cm, the first two digits, 1.5, being read with certainty, and the
third digit, 2, being doubtful or estimated with an uncertainty of
perhaps 1 in that digit or + 0.01 cm overall. Only three digits
are recorded because any more digits to the right would not be valid